The invention pertains to deformable hearing aids. More particularly, the invention pertains to such hearing aids that change shape in response to dynamic changes in the shape of a user""s ear canal.
It has been recognized that, in certain circumstances, hearing aids can significantly improve the quality of life of individuals that have a hearing deficiency. Contemporary hearing aids are often small enough to fit completely into a user""s ear canal. Their small size makes them much more acceptable than older more visible aids.
Despite improvements, there continue to be problems with known hearing aids. Two of these problems are comfort and performance. Contemporary in-the-ear hearing aids usually have an exterior housing molded in accordance with the shape of a user""s ear and ear canal. Such housings are often formed of rigid plastic such as an acrylic.
The rigidness often results in a less than comfortable fit when in place and can produce discomfort during the insertion and removal process. In extreme cases, usually resulting from ear surgery, the shape of the user""s ear or ear canal has been altered such that a conventional hearing aid could not be inserted.
Up to now, there was no economically feasible way to create a compliant hearing aid that was accurately reproducing the ear impression outer features.
Performance is an issue with rigid hearing aids in that the shape of the ear canal changes while talking or eating. This change in shape can compromise the seal formed between the shell and the ear canal. Integrity of this seal is important in minimizing external feedback around the shell. This in turn limits the user""s usable gain and reduces over-all performance of the aid. Maintaining the integrity of this seal makes it possible to operate the aid at higher gain levels, and better compensate for the user""s hearing deficiency providing a higher degree of user satisfaction.
Thus, there continues to be a need for hearing aids that are more comfortable to insert and wear than have heretofore been available. There also continues to be a need for improved performance and higher gain, where appropriate, but without performance degrading external feedback.
A molded, compliant, elastomeric housing for a hearing aid has a shape which is a reproduction of an impression of a portion of a user""s ear canal. When inserted, the housing deforms in accordance with the shape of the ear canal so as to permit comfortable insertion. Once inserted, the reproduced region of the housing sealingly abuts the respective portion of the ear canal so as to provide a seal and prevent feedback. Additionally, the housing deforms in response to deformation of the ear canal as the user moves his or her jaw.
In one embodiment, the housing defines an internal region for an output transducer such as a receiver. The receiver can be located in a mold before the molding step occurs. Alternately, a mandrel, which defines a receiver receiving region, can be positioned in the mold.
Irrespective of whether the receiver is molded in place or if a mandrel is used, a matrix is located in the mold for the housing to displace the receiver and associated wiring inwardly from the mold to form a boundary layer. One usable type of matrix is an open cell foam.
When the mold is filled with the compliant housing material, as described below, the material fills the cells of the foam thereby creating an integral, solid boundary layer. This layer insures that the receiver, and associated wiring, are displaced inwardly from the external periphery of the housing by at least the thickness thereof.
Where a mandrel is used, after curing the housing, removal of the mandrel results in a pre-formed, receiver support pocket displaced inwardly from the exterior periphery by the boundary layer. Additionally, there is a cast channel for the wires to the receiver.
In one aspect, the deformability of the housing makes it possible to mold internal component receiving cavities therein with openings which are too small to permit insertion of the components when the housing is in its normal state. However, in response to a deformation force applied to the respective component, the housing deforms thereby enabling the respective component to slide past the obstruction region and into the premolded component receiving cavity. Components can also be removed by deformation. For example, a receiver could be inserted into a deformable housing at either the audio output end or at the exterior open end of the housing.
The matrix can be inserted into the mold and then components or mandrel inserted. Alternately, the matrix can be wrapped around the components or mandrel and the wrapped combination inserted into the mold.
Use of the matrix insures that neither the respective components nor associated wiring will be too close to the exterior peripheral surface of the housing. They can be no closer than the thickness of the matrix.
Where the matrix is an open cell foam, injection of the elastomer into the mold fills the cells and permits flow of the elastomer to the mold surfaces. A solid peripheral surface and a solid interior, except for predefined cavities, result. Thus, a barrier layer composite of compliant elastomer and filled matrix provides, at least for portions of the housing, the required barrier layer.
A sheet member can be incorporated into the housing so as to minimize the possibility of internal feedback when the respective hearing aid is being used.
The compliant material used for the housing can be silicone, latex, polyurethane, polyvinyl or any other type of time, heat or U.V. curable elastomer. The preferred hardness of the selected elastomers is less than 90 ShoreA.
In accordance with a disclosed method to produce a flexible hearing aid housing:
1. An impression is made of the ear canal and a portion of the outer ear of a respective user and coated with a UV curable plastic or wax to remove imperfections;
2. A female mold is cast using a hydrocolloidal-type material, around at least that part of the impression that extends into the user""s ear canal. Alternately silicones or other elastomers could be used;
3. The ear impression is removed from the female mold;
4. The cavity in the female mold is filled with the same type of material and cured to form a male mold which is a soft, but exact reproduction of the respective part of the ear impression;
5. The male mold can be removed from the female mold as, due to characteristics of the material, the solid female mold does not bond to the liquid poured in to make the male mold even when the male mold has been cured;
6. A coating of UV curable plastic is formed around the compliant male mold and cured so it hardens;
7. The compliant male mold is then removed from the rigid UV cured coating leaving a rigid female mold with a shape that reproduces the respective portions of the user""s ear canal and outer ear;
8. An open cell matrix is inserted into the rigid female mold to create a boundary layer;
9. Mandrels, to define internal regions, or components, such as output transducers, can be positioned in the female mold, or alternatively, the matrix can be wrapped about the mandrels or components prior to insertion;
10. A compliant elastomer is used to fill the female mold encapsulating the mandrels or components and filling the matrix;
11. The housing is then cured by elapsed time, heat, or radiant energy such as UV;
12. The rigid, exterior mold is then removed from the housing and the mandrels are also extracted;
13. Electronic components can then be inserted into the cast regions formed by the mandrels; and
14. A face plate, with battery compartment and electronics can, if appropriate, be attached to the molded housing.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.